1. Field of the Invention
This invention relates to a stable livestock feed premix composition containing antibiotic esters sensitive to acid in solid formulations.
This invention also relates to method for stabilizing an acid-sensitive antibiotic ester by incorporating said ester into a feed premix composition of the invention.
2. Related Disclosure
Certain antibiotic esters are capable of increasing the feed efficiency of livestock, particularly ruminants. For example, laidlomycin propionate and its salts (described in U.S. Pat. No. 4,431,665, incorporated herein by reference in full) is known to increase the feed efficiency of livestock, e.g., swine, poultry, and ruminants, and also to control coccidial infections in livestock, including horses, cattle, poultry, swine, goats and sheep. Such antibiotic esters are preferably administered orally, in either the subject animal's feed or drinking water. When medicaments are to be administered to livestock orally, they are usually first formulated in a "premix," which is then mixed into the livestock's regular feed mixture.
However, certain antibiotic esters are unstable to the acidic conditions usually present in animal feed and premixes. It has now been discovered that, for example, laidlomycin propionate and its salts are most stable in slightly acidic solutions (pH 4-6), but is most stable in solid formulations under basic conditions (pH about 11). We have now discovered that the compositions of the invention economically and effectively stabilize and protect such acid-sensitive antibiotic esters, allowing the incorporation of antibiotics such as laidlomycin esters in livestock feed without the loss of activity.